1. Field of the Invention
The present invention relates to an ink supply system for writing instruments which operate with liquid ink. The housing of the writing instrument, for the writing liquid, has a primary, large-volume reservoir which is preferably under excess pressure, and a secondary, small-volume reservoir which communicates with the outside air and with the writing element; the primary and secondary reservoirs are connected via a recharging valve which can be controlled as a function of need.
2. Description of the Prior Art
Ink supply systems of the aforementioned general type, which conform to a non-published proposal of the assignee of the present invention, exclusively utilize primary ink reservoirs which are at excess pressure. The recharge valve is then a true through-way valve which can be controlled for opening and closing. To the extent that this recharge valve is to be electrically rather than manually operated, and is preferably to be controlled via a sensor which takes advantage of impedance, an electrical power is required which in most cases cannot be furnished by a dry-cell battery accommodated in the housing of the writing instrument.
An object of the present invention therefore is to provide an improved recharge valve for ink supply systems of the aforementioned general type, which valve can be actuated with considerably less electrical energy and can operate without electromagnets, which practically operate in an abrupt manner.